1. Field of the Invention
The present invention relates to communication apparatuses which perform several kinds of coding methods and/or decoding methods, and to methods for operating said apparatuses.
2. Description of the Related Art
As a method for switching a coding method during communication with another communicating party, the following methods are known: A first method performs switching after sending a switching request, and a second method performs switching after receiving a response for a switching request.
However, in the first method, since, because there may be a delay between the time when a sending communication apparatus switches from a first coding method to a second coding method and a time when a receiving communication apparatus switches to a decoding method corresponding to the second coding method, at least some of the audio and/or video data coded using the second coding method may be decoded using an inappropriate decoding method. This can cause problems such as undesired noise and/or turbulence of video.
On the other hand, in the second method, because there is a delay between a time when a receiving communication apparatus switches a decoding method and a time when a sending communication apparatus switches a coding method, the receiving communication apparatus also might decode received audio and/or video data using an inappropriate decoding method, and thus, problems such as noise and/or turbulence of video can also occur in this case.
Thus, recently, a method has been proposed wherein audio and/or video data is muted for a certain period of time when a coding method is switched, and then the audio and/or video data is outputted gradually in order to suppress the occurrence of noise and/or turbulence of video. However, in this method, while the occurrence of noise can be suppressed, another problem can occur in that voice and/or video may be interrupted.
Further, among coding methods or decoding methods, there exists a method that feeds back past information for coding or decoding. In this method, if a coding method or a decoding method is switched before coding processing or decoding processing become stable, problems such as noise and/or turbulence of video can occur.